Ultrasonic focused transducer means of the zone plate type are well known, the operation of which are dependent upon the diffraction phenomenon of acoustic waves and, in particular, upon Fresnel diffraction. One type of acoustic plane transducer includes active areas, or zones, which correspond to the transmissive zones of a Fresnel zone plate, or lens. Such devices may be arranged for energization of the central section or zone, corresponding to a transmissive central zone of a Fresnel zone plate. Alternatively, the central section may be unenergized to correspond to the non-transmissive central zone of a Fresnel zone plate. In a further arrangement, of the type to which the present invention is directed, adjacent zones of the transducer are energized in 180.degree. out of phase relationship whereby both the "in-phase", and "out of phase" regions, or zones, are active for increased power sensitivity or output, and for better approximation to a perfect focus. Prior art transducers of this general type are shown, for example, in U.S. Pat. No. 2,875,355 issued Feb. 4, 1959, and in an article by S. A. Farnow and B. A. Auld, entitled "An Acoustic Phase Plate Imaging Device" presented at The Sixth International Symposium on Acoustical Holography and Imaging, Feb. 4-7, 1975 at San Diego, CA.
Various arrangements for providing for adjacent active zones within the transducer body are known. In one such arrangement the transducer body is uniformly poled and the individual zones are shunt-connected in proper phase relationship to obtain adjacent active zones. In another arrangement, the adjacent zones are oppositely polarized and single electrodes are provided at opposite faces thereof. With such prior art arrangements shunt connection is made to the zones thereby resulting in a low impedance transducer difficult to match to the impedance of an rf drive source, or a receiver.